Linear bearing for an electromagnetic solenoid and solenoid having said linear bearing

ABSTRACT

A rolling-element bearing for an electromagnetic solenoid includes a hollow cylindrical cage with a plurality of spherical pockets formed around a first circumference and a second circumference of the cage. The pockets around the first circumference are offset from the pockets around the second circumference. Spherical rolling elements are provided in the spherical pockets and are captured for free rotation in the first pockets and second pockets.

FIELD OF INVENTION

Embodiments of the present invention generally relate to a linear motionbearing for electromagnetic solenoids.

BACKGROUND

Solenoids generally include a movable armature and a stationary polepiece with a pin couple to the armature and supported for lineardisplacement by a bushing in the pole piece. However, somesolenoid-activated systems require less friction and greater toleranceto contamination than can be provided by a system including a bushing.

Accordingly, a need exists for a bearing to reduce friction and improvetolerance to contamination in an electromagnetic solenoid.

SUMMARY

Embodiments of a bearing with reduced friction and improved tolerance tocontamination (robustness) are provided herein. In some embodiments, acage for a rolling-element bearing for an electromagnetic solenoidcomprises a plurality of spherical first pockets formed around a firstcircumference of the cage on a first pitch diameter and a plurality ofspherical second pockets formed around a second circumference of thecage axially offset from the first circumference on a second pitchdiameter, which may be equal to the first pitch diameter. The firstpockets are angularly offset from the second pockets so the pockets.

In some embodiments, a rolling-element bearing for an electromagneticsolenoid comprises a cage including a plurality of spherical firstpockets formed around a first circumference of a hollow cylindrical cageon a first pitch diameter. A plurality of spherical second pocketsformed around a second circumference of the cage is axially offset fromthe first circumference on a second pitch diameter, which may be equalto the first pitch diameter, with the first pockets angularly offsetfrom the second pockets. A plurality of spherical rolling elements isprovided, one of the plurality captured for free rotation in each of theplurality of spherical first pockets and in each of the plurality ofspherical second pockets.

In some embodiments, an electromagnetic solenoid comprises a flux sleevedisposed within a housing, a pole piece disposed within the housingaxially aligned and spaced apart from the flux sleeve, the pole pieceincluding a recess in the end adjacent to the flux sleeve and an axialbore through a length of the pole piece. An armature is disposed withinthe flux sleeve supported for axial displacement with a centrallylocated pin fixed to an end portion of the armature proximate to thepole piece for axial displacement with the armature. A rolling-elementbearing is disposed for free movement within the axial bore including,the rolling-element bearing including a cage including a plurality ofspherical first pockets formed around a first circumference of the cageon a first pitch diameter and a plurality of spherical second pocketsformed around a second circumference of the cage axially offset from thefirst circumference on a second pitch diameter, which may be equal tothe first pitch diameter, the first pockets angularly offset from thesecond pockets. A plurality of spherical rolling elements, one of theplurality is captured for free rotation in each of the plurality ofspherical first pockets and in each of the plurality of spherical secondpockets. The pin is accepted within the hollow cylindrical cage andsupported on one or more of the spherical rolling elements.

Other and further embodiments of the present invention are describedbelow.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention, briefly summarized above anddiscussed in greater detail below, can be understood by reference to theillustrative embodiments of the invention depicted in the appendeddrawings. It is to be noted, however, that the appended drawingsillustrate only typical embodiments of this invention and are thereforenot to be considered limiting of its scope, for the invention may admitto other equally effective embodiments.

FIG. 1 is a perspective view depicting a rolling element cage inaccordance with an embodiment of the present invention.

FIG. 1A depicts a cross-sectional view of the rolling element cage ofFIG. 1 taken at circumference 106.

FIG. 1B depicts a cross-sectional view of the rolling element cage ofFIG. 1 taken at circumference 116.

FIG. 2 depicts an exploded view of the rolling element cage of FIG. 1

FIG. 3 depicts a perspective view of a rolling-element bearing accordingto an embodiment of the present invention.

FIG. 4 depicts a longitudinal section of the rolling-element bearing ofFIG. 3 taken along line IV-IV.

FIG. 5 depicts an exploded view of a rolling-element bearing inaccordance with an embodiment of the present invention.

FIG. 6A depicts a perspective view of a rolling-element bearingaccording to an embodiment of the present invention.

FIG. 6B depicts an exploded view of the rolling-element bearing of 6A.

FIG. 7 schematically depicts a solenoid including a rolling elementbearing in accordance with an embodiment of the present invention.

FIG. 8 schematically depicts a solenoid including two rolling elementbearings in accordance with an embodiment of the present invention

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common inthe figures. The figures are not drawn to scale and may be simplifiedfor clarity. It is contemplated that elements and features of oneembodiment may be beneficially incorporated in other embodiments withoutfurther recitation.

While the present invention may be described in reference to anautomotive system, the present invention may be modified for a varietyof applications while remaining within the spirit and scope of theclaimed invention, since the range of the potential applications isgreat, and because it is intended that the present invention beadaptable to many such variations.

DETAILED DESCRIPTION

FIG. 1 depicts an exemplary non-magnetic rolling-element cage, cage 100,comprising a hollow cylindrical body 102 comprising a plurality of firstspherical pockets, first pockets 104, formed in the plane of a firstcircumference 106. The cage 100 may be formed from one or morenon-magnetic metals, such as brass, some stainless steels, or from oneor more non-magnetic materials, such as plastic materials.

A plurality of second spherical pockets, second pockets 114, is formedin the plane of a second circumference 116. As used throughout thisdisclosure, “spherical pockets” or “semi-spherical pockets” arespherically shaped, i.e., the walls of the pockets are portions of aspherical surface. This may include a plurality of features formed on aportion of the cage 100 adjacent to the first and second pockets 104,114 configured to create at least a partial spherical surface.

The planes of the first circumference 106 and the second circumference116 are parallel and separated in an axial direction corresponding toaxis 120 by a distance 122. For ease of illustration, the non-limitingembodiment of FIG. 1 depicts three first pockets 104 in the plane of thefirst circumference 106 and three second pockets 114 (2 are hidden) inthe plane of the second circumference 116 (as may be understood fromFIGS. 1A, 1B, and 2). However, other embodiments may have two first orsecond pockets, or more than three first or second pockets, and thenumber of first pockets may be different than the number of secondpockets.

The centers of each of the first pockets 104 lie on a pitch circle 108as illustrated in FIG. 1A. Similarly, the centers of each of the secondpockets 114 lie on a second pitch circle 118 as shown in FIG. 1B. Asused herein, a pitch circle (i.e., first pitch circle 108 or secondpitch circle 118) is a circle formed through the center points of eachof the pockets (i.e., first pockets 104 or second pockets 114).

The first pockets 104 are angularly offset from the second pockets 114when viewed along axis 120. As illustrated, the three first pockets 104are evenly, or substantially evenly spaced around the first pitch circle108 by and angle A and the three second pockets 114 are similarly evenlyor substantially evenly spaced around the second pitch circle 118 by andangle B. As such, adjacent first pockets 104 (or second pockets 114) areangularly spaced apart by the angle A (or angle B) of about 120 degreesfrom each other. The first pockets 104 are evenly, or substantiallyevenly, angularly offset from second pockets 114. Accordingly, in thenon-limiting embodiment illustrated, the first pockets 104 are radiallyoffset form the second pockets 114 by 60 degrees. In other embodiment,the offset may be greater than 60 degrees or less than 60 degrees.

In the non-limiting embodiments of FIG. 2, the cage 100 comprises twohollow cylindrical halves, first half 124 and second half 126, which areidentical according to the embodiment illustrated, but are notnecessarily identical. As illustrated in FIGS. 1A and 1B, first half 124and second half 126 have an inner diameter D1 and an outer diameter D2and a wall thickness T between the inner wall 103 and outer wall 105.The first half 124 has a first side 204 including a plurality of evenlyspaced first projections 208 (3 shown) and evenly spaced first recesses212 (3 shown). The second half 126 has a first side 206 including aplurality of evenly spaced second projection 210 (3 shown) and evenlyspaced second recess 214 (3 shown). As illustrated the first projections208 and first recesses 212 and the second projection 210 and secondrecess 214 are equal in number, although they need not be equal innumber.

At least some of the second projection 210 includes a semi-sphericalpocket 216 (i.e., one half of the spherically shaped first pocket 104)formed on an edge 109 of the wall thickness T. At least some secondrecess 214 includes a semi-spherical pocket 218 (i.e., one half of thespherically shaped second pocket 114) formed on an edge 111.

At least some first projection 208 includes a semispherical pocket 220formed on an edge 115 of the wall thickness T. At least some firstrecess 212 includes a semi-spherical pocket 222 (i.e., one half of thespherically shaped first pocket 104) formed on the edge 113 of the wallthickness T. Each of the semi-spherical pockets 216, 218, 220, 222 iscentrally located at a midpoint of the wall thickness T.

The first and second recesses 212, 214 may be formed as the negative ofthe first and second projections 208, 210 so that the first and secondprojections 208, 210 can be inserted into the first and second recesses212, 214 (i.e., the recesses 212, 214 receive the projections 208, 210).As such, in some embodiments, a first half 124 and a second half 126 canbe positioned with first and second projections 208, 210, respectively,in opposition (i.e., facing each other) and brought together such thatthe first projections 208 are aligned with the second recesses 214 andthe first recesses 212 are aligned with second projections 210.

When the first projections 208 and second projections 210 and the firstrecesses 212 and second recesses 214 are brought together as describedabove, the semi-spherical pockets 220 in the first projections 208 arealigned with the second semi-spherical pockets 218 in the second recess214 and together form the spherical second pocket 114. Likewise, thesemi-spherical pockets 222 in the first recess 212 are aligned with thesemi-spherical pockets 216 in the associated second projections 210 andtogether form the spherical first pockets 104.

A plurality of spherical rolling elements 302, for example ballbearings, is disposed in the first pockets 104 and the second pockets114 and captured for free rotation within the spherical pockets. Therolling elements 302 have a diameter 304 greater than the wall thicknessT. The first and second pockets 104, 114 are positioned in the wallthickness T such that a first portion 308 of each of the plurality ofspherical rolling elements 302 extends radially outwardly from the outerwall 105 of the cage 100 and a second portion 310 of each of theplurality of spherical rolling elements 302 extends radially inwardlyfrom the inner wall 103.

The spherical rolling elements 302 may be placed in upwardly directedsemi-spherical pockets, for example second semi-spherical pockets 216,218 as illustrated in FIG. 5. First half 124 and second half 126,positioned as above such that the projections and recesses are alignedand brought into engagement, form the spherical first and second pockets104, 114 and capture the spherical rolling elements 302 for freerotation.

In other embodiments, the cage may be a stamped metal constructionformed from a plurality of stamped metal components assembled to yieldpockets configured to capture spherical rolling elements as describedabove. In other embodiments, the cage may be formed from one or moremolded, stamped, or otherwise formed metal or plastic componentsconfigures to capture a plurality of spherical rolling elements for freerotation in two or more planes, with the rolling elements in adjacentplanes disposed in a radially staggered orientation.

For example, FIG. 6A depicts a rolling element bearing 600 comprising acylindrical cage 602 capturing spherical rolling elements 302 for freerotation in spherical pockets 603 formed on a first pitch diameter andan equal plurality of pockets 605 formed on a second pitch diameter. Thecylindrical cage 602 is formed from molded or stamped elements 604, 606which are which are identical, including equal pitch diameters,according to the embodiment illustrated, but are not necessarilyidentical. Elements 604, 606 are non-magnetic, and may be formed fromany of the material discussed above.

FIG. 6B depicts an exploded view of the rolling element bearing 600 forclarity. Similar to the embodiments discussed above, the plurality ofspherical pockets 603 and 605 are partially formed by details inelements 604 and 606. As illustrated, element 604 has a plurality ofsemi-spherical pockets 608, open downward, formed in the plane of acircumference 610 and an equal plurality of semi-spherical pockets 612,also open downward, formed in the plane of a circumference 614 spacedapart from the plane of circumference 610.

Similar to element 604, element 606 has a plurality of semi-sphericalpockets 616 formed in the plane of a circumference 618 and a pluralityof semi-spherical pockets 620 formed in the plane of circumference 622.Element 606 is element 604 inverted so that the semi-spherical pockets608 and 612 are open upward and rotated such that semi-spherical pockets616 and 620 align with semi-spherical pockets 608 and 612 of element604.

As illustrated in FIG. 6B, spherical rolling elements 302 can be placedin upward facing semi-spherical pockets 616 and 620. Element 604 and 606can then be brought into engagement such that semi-spherical pockets 608and 616 form spherical pocket 603 and semi-spherical pockets 612 and 620form spherical pocket 605. Spherical rolling elements 302 are capturedfor free rotation in the spherical pockets 603, 605.

Elements 604, 606 may be joined together in any known manner, such asadhesive bonding, welding, heat staking, or the like.

The cages 100, 602 assembled as described in the embodiments above withspherical rolling elements 302 captured for free rotation within thepockets 104, 114 or 603, 605 forms a rolling-element bearing 300 or 600as shown in FIGS. 3 and 6 suitable for use in an electromagneticsolenoid according to embodiments of this invention.

FIG. 7 depicts a non-limiting embodiment of an electromechanicalsolenoid, solenoid 700, including rolling-element bearing 300,600, inaccordance with an embodiment of the present invention. The solenoid 700is shown in a simplified, schematic form for clarity.

The solenoid 700 includes a flux sleeve 704 and a pole piece 706 alignedand coaxially disposed in a spaced apart relationship within a housing702. The pole piece 706 has a first end 708 adjacent to the flux sleeve704 including a recess 710. The pole piece 706 includes an axial bore712 through the length of the pole piece 706. The axial bore 712 asillustrated includes a first portion 714 having a first diameter and asecond portion 716 having a larger diameter than the first portion 714.A ledge 718 is formed in the area where the first portion 714 and thesecond portion 716 meet.

An armature 720 is disposed and supported for axial displacement withinthe flux sleeve 704. As illustrated, a portion of the armature 720 mayextend beyond the flux sleeve 704 at a point in the axial displacementof the armature 720. At least the end portion 722 of the armature 720 issized to be at least partially received within the recess 710 in thepole piece 706.

A non-magnetic pin, pin 724, is coupled to at least the end portion 722of the armature 720, for example by a press fit or other mechanicalattachment, for axial displacement with the armature 720. The pin 724extends beyond the end portion 722 of the armature and into and throughthe length of the pole piece 706. A rolling-element bearing 300,600 isdisposed for free axial and radial movement within the axial bore 712 inthe second portion 716, and accepts and supports a portion of the pin724. As discussed above, second portions 310 of the spherical rollingelements 302 extend radially inwardly from the inner wall 103 of thecage 100,602. The pin 724 rests on at least some of the sphericalrolling elements 302 on the second portion 310.

A bearing stop 726 is provided at the end of the second portion 716adjacent to the armature 720 with the bearing stop 726 disposed at leastpartially within the second portion 716. A first end 728 of the bearingstop 726 provides a first limit to the axial displacement of therolling-element bearing 300,600 within the second portion 716. A secondlimit to the axial displacement of the rolling-element bearing 300,600is provided by the ledge 718. Accordingly, the free movement of therolling-element bearing 300,600 is limited by the first end 728 of thebearing stop 726 and the ledge 718.

As the armature 720 is displaced axially within the flux sleeve 704 andat least partially within the recess 710 of the pole piece 706, the pin724 is displaced a corresponding amount. Because the pin 724 issupported on the spherical rolling elements 302, as the pin 724 isdisplaced, the spherical rolling elements 302 roll with the pin 724.Because the spherical rolling elements 302 are captured within thespherical first and second pockets 104, 114, the rolling-element bearing300,600 is also displaced within the second portion 716.

Axial displacement of the armature 720 is limited in a first direction(toward the pole piece 706) by a second end 730 of the bearing stop 726disposed in the recess 710. The second end 730 provides a physical stopfor the armature 720 and also prevents the armature 720 from contactingthe pole piece (“latching”). Axial displacement of the armature 720 in asecond direction, opposite the first direction, is limited by an end cap(not shown) at an end of the flux sleeve 704 opposite the pole piece706.

FIG. 8 depicts a non-limiting embodiment of an electromechanicalsolenoid, solenoid 800, including many of the features of solenoid 700.Solenoid 800 includes a rolling-element bearing 806 at the back side 802of the armature 720 in a pocket 804 between a larger diameter portion ofthe flux sleeve 704 and the armature 720. The rolling-element bearing806 may be of similar construction to either of the rolling-elementbearings 300 or 600. The rolling-element bearing 806 has an innerdiameter suitable to accept the armature 720 and an outer diametersuitable to fit within the pocket 804.

The rolling-element bearing 806 has been observed to provide guidance tothe back side 802 of the armature 720 in linear travel and generallyreduce the friction in the solenoid 800.

The inventor has observed that placing a plurality of spherical rollingelements in pockets arranged in parallel planes, and radially offsettingthe pockets between adjacent planes, substantially reduces the tendencyof the rolling-element bearing from tipping in the pole piece. Tippingof the bearing has been observed to cause contact between the pin andthe pole piece or possibly binding between the spherical rollingelements and the pin. Either condition increases the resistance to axialdisplacement of the armature.

Thus a cage for an electromagnetic solenoid, a bearing using the cage,and an electromagnetic solenoid using the bearing are provided herein.The inventive bearing may advantageously reduce friction and increasesolenoid robustness against contamination.

What is claimed is:
 1. A cage for a rolling-element bearing for anelectromagnetic solenoid comprising: a hollow cylindrical body; aplurality of spherical first pockets formed around a first circumferenceof the hollow cylindrical body on a first pitch diameter; and aplurality of spherical second pockets formed around a secondcircumference of the hollow cylindrical body axially offset from thefirst circumference on a second pitch diameter equal to the first pitchdiameter, wherein the first pockets are angularly offset from the secondpockets.
 2. The cage of claim 1, wherein the cage comprises a firsthollow cylindrical half having a wall thickness and a second hollowcylindrical half having a wall thickness, each half having on a firstside a plurality of evenly spaced projections and a same plurality ofevenly spaced recesses formed as a negative of the projections, eachprojection and each recess including a semi-spherical pocket formed onan edge of the wall thickness such that the first half and the secondhalf positioned with first sides in opposition can be assembled togetherwith the projections of the first half accepted into the recesses of thesecond half and the semi-spherical pocket align to form the plurality ofspherical first pockets and the plurality of spherical second pockets.3. The cage of claim 2, wherein the first hollow cylindrical half andthe second hollow cylindrical half are identical.
 4. The cage of claim2, wherein each of the semi-spherical pocket is centrally located at amidpoint of the wall thickness.
 5. The cage of claim 2, wherein the cageis formed from a non-magnetic material.
 6. A rolling-element bearing foran electromagnetic solenoid comprising: a hollow cylindrical cage havinga wall thickness and including a plurality of spherical first pocketsformed around a first circumference of the cage on a first pitchdiameter; and a plurality of spherical second pockets formed around asecond circumference of the cage axially offset from the firstcircumference on a second pitch diameter, the first pockets angularlyoffset from the second pockets; and a plurality of spherical rollingelements, one of the plurality captured for free rotation in one of theplurality of spherical first pockets and one of the plurality capturedfor free rotation in one of the plurality of spherical second pockets.7. The bearing of claim 6, wherein the cage comprises a first hollowcylindrical half having a wall thickness and a second cylindrical halfhaving a wall thickness, each half having on a first side a plurality ofevenly spaced projections and a same plurality of evenly spaced recessesformed as a negative of the projections, each projection and each recessincluding a semi-spherical pocket formed on an edge of the wallthickness such that the first half and the second half positioned withfirst sides in opposition and brought together such that the projectionsof the first half are accepted into the recesses of the second half andthe semi-spherical pockets align to form the plurality of sphericalfirst pockets and the plurality of spherical second pockets, and thefirst half and the second half are joined together.
 8. The bearing ofclaim 6, wherein the cage is formed from plastic.
 9. The bearing ofclaim 6, wherein the cage is a stamped metal construction formed from anon-magnetic metal.
 10. The bearing of claim 6, wherein a diameter ofeach the plurality of spherical rolling elements is greater than thewall thickness.
 11. The bearing of claim 6, wherein a first portion ofeach of the plurality of spherical rolling elements extends radiallyoutwardly from an outer wall of the cage and a second portion of each ofthe plurality of spherical rolling elements extends radially inwardlyfrom an inner wall of the cage.
 12. The bearing of claim 6, wherein thefirst pitch diameter is equal to the second pitch diameter.
 13. Anelectromagnetic solenoid comprising: a flux sleeve disposed within ahousing; a pole piece disposed within the housing axially aligned andspaced apart from the flux sleeve, the pole piece including a recess inan end adjacent to the flux sleeve and an axial bore through a length ofthe pole piece; an armature disposed within the flux sleeve supportedfor axial displacement; a centrally located pin fixed to an end portionof the armature proximate to the pole piece for axial displacement withthe armature; and a first rolling-element bearing disposed for freemovement within the axial bore including: a hollow cylindrical cageincluding a plurality of spherical first pockets formed around a firstcircumference of the cage on a first pitch diameter; a plurality ofspherical second pockets formed around a second circumference of thecage axially offset from the first circumference on a second pitchdiameter equal to the first pitch diameter, the first pockets angularlyoffset from the second pockets; and a plurality of spherical rollingelement, one captured for free rotation in each of the plurality ofspherical first pockets and in each of the plurality of spherical secondpockets, wherein the pin is accepted within the hollow cylindrical cageand supported on one or more of the spherical rolling elements.
 14. Thesolenoid of claim 13, wherein the axial bore includes a first portionhaving a first diameter and a second portion having a larger seconddiameter adjacent the recess and forming a ledge.
 15. The solenoid ofclaim 14, wherein the rolling-element bearing is disposed in the secondportion of the axial bore.
 16. The solenoid of claim 15, furthercomprising a bearing stop disposed at least partially in the secondportion.
 17. The solenoid of claim 16, wherein the free movement of therolling-element bearing includes axial displacement in the secondportion between a first end of the bearing stop and the ledge.
 18. Thesolenoid of claim 16, wherein the axial displacement of the armature islimited by a second end of the bearing stop disposed in the recessproviding a physical stop.
 19. The solenoid of claim 13, furthercomprising: a second rolling-element bearing disposed for free movementwithin the axial bore including: a hollow cylindrical cage including aplurality of spherical first pockets formed around a first circumferenceof the cage on a first pitch diameter; a plurality of spherical secondpockets formed around a second circumference of the cage axially offsetfrom the first circumference on a second pitch diameter equal to thefirst pitch diameter, the first pockets angularly offset from the secondpockets; and a plurality of spherical rolling element, one captured forfree rotation in each of the plurality of spherical first pockets and ineach of the plurality of spherical second pockets, wherein the pin isaccepted within the hollow cylindrical cage and supported on one or moreof the spherical rolling elements.
 20. The solenoid of claim 13, whereinthe hollow cylindrical cage comprises a first hollow cylindrical halfhaving a wall thickness and a second cylindrical half having a wallthickness, each half having on a first side a plurality of evenly spacedprojections and a same plurality of evenly spaced recesses formed as anegative of the projections, each projection and each recess including asemi-spherical pocket formed on an edge of the wall thickness such thatthe first half and the second half positioned with first sides inopposition and brought together such that the projections of the firsthalf are accepted into the recesses of the second half and thesemi-spherical pockets align to form the plurality of spherical firstpockets and the plurality of spherical second pockets, and the firsthalf and the second half are joined together.